What about a enemy whose stats and level scale off the PC's level? You would probably need several equations for different level brackets, but it could be the ideal leveling partner. Make it a miniboss with giant, and it could vary well be the leveler's challenge.
Rift is perfectly viable for second life plus, when you could become top tier at low levels with minimal effort. On first life, despite my various attempts, its become something of a exercise in frustration. I can defeat rift stuff at low level, but not consistently enough to validate the xp gain, which despite being relatively good is still lacking without underdog. Plus, since children are no longer the promised gateway to ascension godhood, i feel a bit pressured to grind until i drop, which feels very stressful.